[dev.link] cmd/link/internal/objfile: relocate loader to new package

Third change of several to update the loader API to reflect the final
consensus version of the loader API as described in Cherry's doc.
This piece:

   - move objfile.Loader into its own separate package, and update
     clients accordingly.

This includes a few minor cleanups, including converting a couple
of loader-related functions to methods, and privatizing some of the
loader methods such as ToGlobal/ToLocal.

Change-Id: Iae20585751a45491d8b19dcffc096aadae6bbfc6
Reviewed-on: https://go-review.googlesource.com/c/go/+/200998
Run-TryBot: Than McIntosh <thanm@google.com>
Reviewed-by: Jeremy Faller <jeremy@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/cmd/dist/buildtool.go

@@ -73,6 +73,7 @@ var bootstrapDirs = []string{
 	"cmd/link/internal/arm64",
 	"cmd/link/internal/ld",
 	"cmd/link/internal/loadelf",
+	"cmd/link/internal/loader",
 	"cmd/link/internal/loadmacho",
 	"cmd/link/internal/loadpe",
 	"cmd/link/internal/loadxcoff",

src/cmd/link/internal/ld/lib.go

@@ -38,6 +38,7 @@ import (
 	"cmd/internal/objabi"
 	"cmd/internal/sys"
 	"cmd/link/internal/loadelf"
+	"cmd/link/internal/loader"
 	"cmd/link/internal/loadmacho"
 	"cmd/link/internal/loadpe"
 	"cmd/link/internal/loadxcoff"
@@ -376,7 +377,7 @@ func (ctxt *Link) findLibPath(libname string) string {
 
 func (ctxt *Link) loadlib() {
 	if *flagNewobj {
-		ctxt.loader = objfile.NewLoader()
+		ctxt.loader = loader.NewLoader()
 	}
 
 	ctxt.cgo_export_static = make(map[string]bool)
@@ -434,7 +435,7 @@ func (ctxt *Link) loadlib() {
 
 	if *flagNewobj {
 		// Add references of externally defined symbols.
-		objfile.LoadRefs(ctxt.loader, ctxt.Arch, ctxt.Syms)
+		ctxt.loader.LoadRefs(ctxt.Arch, ctxt.Syms)
 	}
 
 	// Now that we know the link mode, set the dynexp list.
@@ -1772,7 +1773,7 @@ func ldobj(ctxt *Link, f *bio.Reader, lib *sym.Library, length int64, pn string,
 	}
 	var c int
 	if *flagNewobj {
-		objfile.LoadNew(ctxt.loader, ctxt.Arch, ctxt.Syms, f, lib, unit, eof-f.Offset(), pn, flags)
+		ctxt.loader.Preload(ctxt.Arch, ctxt.Syms, f, lib, unit, eof-f.Offset(), pn, flags)
 	} else {
 		c = objfile.Load(ctxt.Arch, ctxt.Syms, f, lib, unit, eof-f.Offset(), pn, flags)
 	}
@@ -2550,7 +2551,7 @@ func dfs(lib *sym.Library, mark map[*sym.Library]markKind, order *[]*sym.Library
 
 func (ctxt *Link) loadlibfull() {
 	// Load full symbol contents, resolve indexed references.
-	objfile.LoadFull(ctxt.loader, ctxt.Arch, ctxt.Syms)
+	ctxt.loader.LoadFull(ctxt.Arch, ctxt.Syms)
 
 	// For now, add all symbols to ctxt.Syms.
 	for _, s := range ctxt.loader.Syms {

src/cmd/link/internal/ld/link.go

@@ -35,7 +35,7 @@ import (
 	"cmd/internal/obj"
 	"cmd/internal/objabi"
 	"cmd/internal/sys"
-	"cmd/link/internal/objfile"
+	"cmd/link/internal/loader"
 	"cmd/link/internal/sym"
 	"debug/elf"
 	"fmt"
@@ -98,7 +98,7 @@ type Link struct {
 
 	relocbuf []byte // temporary buffer for applying relocations
 
-	loader  *objfile.Loader
+	loader  *loader.Loader
 	cgodata []cgodata // cgo directives to load, three strings are args for loadcgo
 
 	cgo_export_static  map[string]bool

src/cmd/link/internal/objfile/objfile2.go → src/cmd/link/internal/loader/loader.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-package objfile
+package loader
 
 import (
 	"bytes"
@@ -87,8 +87,6 @@ func makeBitmap(n int) bitmap {
 }
 
 // A Loader loads new object files and resolves indexed symbol references.
-//
-// TODO: describe local-global index mapping.
 type Loader struct {
 	start    map[*oReader]Sym // map from object file to its start index
 	objs     []objIdx         // sorted by start index (i.e. objIdx.i)
@@ -117,12 +115,12 @@ func NewLoader() *Loader {
 }
 
 // Return the start index in the global index space for a given object file.
-func (l *Loader) StartIndex(r *oReader) Sym {
+func (l *Loader) startIndex(r *oReader) Sym {
 	return l.start[r]
 }
 
 // Add object file r, return the start index.
-func (l *Loader) AddObj(pkg string, r *oReader) Sym {
+func (l *Loader) addObj(pkg string, r *oReader) Sym {
 	if _, ok := l.start[r]; ok {
 		panic("already added")
 	}
@@ -148,10 +146,10 @@ func (l *Loader) AddSym(name string, ver int, i Sym, r *oReader, dupok bool, typ
 		if dupok {
 			return false
 		}
-		overwrite := r.DataSize(int(i-l.StartIndex(r))) != 0
+		overwrite := r.DataSize(int(i-l.startIndex(r))) != 0
 		if overwrite {
 			// new symbol overwrites old symbol.
-			oldr, li := l.ToLocal(oldi)
+			oldr, li := l.toLocal(oldi)
 			oldsym := goobj2.Sym{}
 			oldsym.Read(oldr.Reader, oldr.SymOff(li))
 			oldtyp := sym.AbiSymKindToSymKind[objabi.SymKind(oldsym.Type)]
@@ -190,8 +188,8 @@ func (l *Loader) AddExtSym(name string, ver int) Sym {
 }
 
 // Convert a local index to a global index.
-func (l *Loader) ToGlobal(r *oReader, i int) Sym {
-	g := l.StartIndex(r) + Sym(i)
+func (l *Loader) toGlobal(r *oReader, i int) Sym {
+	g := l.startIndex(r) + Sym(i)
 	if ov, ok := l.overwrite[g]; ok {
 		return ov
 	}
@@ -199,7 +197,7 @@ func (l *Loader) ToGlobal(r *oReader, i int) Sym {
 }
 
 // Convert a global index to a local index.
-func (l *Loader) ToLocal(i Sym) (*oReader, int) {
+func (l *Loader) toLocal(i Sym) (*oReader, int) {
 	if ov, ok := l.overwrite[i]; ok {
 		i = ov
 	}
@@ -216,7 +214,7 @@ func (l *Loader) ToLocal(i Sym) (*oReader, int) {
 }
 
 // Resolve a local symbol reference. Return global index.
-func (l *Loader) Resolve(r *oReader, s goobj2.SymRef) Sym {
+func (l *Loader) resolve(r *oReader, s goobj2.SymRef) Sym {
 	var rr *oReader
 	switch p := s.PkgIdx; p {
 	case goobj2.PkgIdxInvalid:
@@ -245,7 +243,7 @@ func (l *Loader) Resolve(r *oReader, s goobj2.SymRef) Sym {
 			log.Fatalf("reference of nonexisted package %s, from %v", pkg, r.unit.Lib)
 		}
 	}
-	return l.ToGlobal(rr, int(s.SymIdx))
+	return l.toGlobal(rr, int(s.SymIdx))
 }
 
 // Look up a symbol by name, return global index, or 0 if not found.
@@ -266,7 +264,7 @@ func (l *Loader) RawSymName(i Sym) string {
 	if l.extStart != 0 && i >= l.extStart {
 		return ""
 	}
-	r, li := l.ToLocal(i)
+	r, li := l.toLocal(i)
 	osym := goobj2.Sym{}
 	osym.Read(r.Reader, r.SymOff(li))
 	return osym.Name
@@ -277,7 +275,7 @@ func (l *Loader) SymName(i Sym) string {
 	if l.extStart != 0 && i >= l.extStart {
 		return ""
 	}
-	r, li := l.ToLocal(i)
+	r, li := l.toLocal(i)
 	osym := goobj2.Sym{}
 	osym.Read(r.Reader, r.SymOff(li))
 	return strings.Replace(osym.Name, "\"\".", r.pkgprefix, -1)
@@ -288,7 +286,7 @@ func (l *Loader) SymType(i Sym) sym.SymKind {
 	if l.extStart != 0 && i >= l.extStart {
 		return 0
 	}
-	r, li := l.ToLocal(i)
+	r, li := l.toLocal(i)
 	osym := goobj2.Sym{}
 	osym.Read(r.Reader, r.SymOff(li))
 	return sym.AbiSymKindToSymKind[objabi.SymKind(osym.Type)]
@@ -299,7 +297,7 @@ func (l *Loader) SymAttr(i Sym) uint8 {
 	if l.extStart != 0 && i >= l.extStart {
 		return 0
 	}
-	r, li := l.ToLocal(i)
+	r, li := l.toLocal(i)
 	osym := goobj2.Sym{}
 	osym.Read(r.Reader, r.SymOff(li))
 	return osym.Flag
@@ -315,7 +313,7 @@ func (l *Loader) Data(i Sym) []byte {
 	if l.extStart != 0 && i >= l.extStart {
 		return nil
 	}
-	r, li := l.ToLocal(i)
+	r, li := l.toLocal(i)
 	return r.Data(li)
 }
 
@@ -324,7 +322,7 @@ func (l *Loader) NAux(i Sym) int {
 	if l.extStart != 0 && i >= l.extStart {
 		return 0
 	}
-	r, li := l.ToLocal(i)
+	r, li := l.toLocal(i)
 	return r.NAux(li)
 }
 
@@ -334,10 +332,10 @@ func (l *Loader) AuxSym(i Sym, j int) Sym {
 	if l.extStart != 0 && i >= l.extStart {
 		return 0
 	}
-	r, li := l.ToLocal(i)
+	r, li := l.toLocal(i)
 	a := goobj2.Aux{}
 	a.Read(r.Reader, r.AuxOff(li, j))
-	return l.Resolve(r, a.Sym)
+	return l.resolve(r, a.Sym)
 }
 
 // Initialize Reachable bitmap for running deadcode pass.
@@ -349,7 +347,7 @@ func (l *Loader) InitReachable() {
 func (relocs *Relocs) At(j int) Reloc {
 	rel := goobj2.Reloc{}
 	rel.Read(relocs.r.Reader, relocs.r.RelocOff(relocs.li, j))
-	target := relocs.l.Resolve(relocs.r, rel.Sym)
+	target := relocs.l.resolve(relocs.r, rel.Sym)
 	return Reloc{
 		Off:  rel.Off,
 		Size: rel.Siz,
@@ -364,7 +362,7 @@ func (l *Loader) Relocs(i Sym) Relocs {
 	if l.extStart != 0 && i >= l.extStart {
 		return Relocs{}
 	}
-	r, li := l.ToLocal(i)
+	r, li := l.toLocal(i)
 	return l.relocs(r, li)
 }
 
@@ -380,7 +378,7 @@ func (l *Loader) relocs(r *oReader, li int) Relocs {
 
 // Preload a package: add autolibs, add symbols to the symbol table.
 // Does not read symbol data yet.
-func LoadNew(l *Loader, arch *sys.Arch, syms *sym.Symbols, f *bio.Reader, lib *sym.Library, unit *sym.CompilationUnit, length int64, pn string, flags int) {
+func (l *Loader) Preload(arch *sys.Arch, syms *sym.Symbols, f *bio.Reader, lib *sym.Library, unit *sym.CompilationUnit, length int64, pn string, flags int) {
 	roObject, readonly, err := f.Slice(uint64(length))
 	if err != nil {
 		log.Fatal("cannot read object file:", err)
@@ -403,7 +401,7 @@ func LoadNew(l *Loader, arch *sys.Arch, syms *sym.Symbols, f *bio.Reader, lib *s
 		unit.DWARFFileTable[i] = r.DwarfFile(i)
 	}
 
-	istart := l.AddObj(lib.Pkg, or)
+	istart := l.addObj(lib.Pkg, or)
 
 	ndef := r.NSym()
 	nnonpkgdef := r.NNonpkgdef()
@@ -425,7 +423,7 @@ func LoadNew(l *Loader, arch *sys.Arch, syms *sym.Symbols, f *bio.Reader, lib *s
 
 // Make sure referenced symbols are added. Most of them should already be added.
 // This should only be needed for referenced external symbols.
-func LoadRefs(l *Loader, arch *sys.Arch, syms *sym.Symbols) {
+func (l *Loader) LoadRefs(arch *sys.Arch, syms *sym.Symbols) {
 	for _, o := range l.objs[1:] {
 		loadObjRefs(l, o.r, arch, syms)
 	}
@@ -479,7 +477,7 @@ func preprocess(arch *sys.Arch, s *sym.Symbol) {
 }
 
 // Load full contents.
-func LoadFull(l *Loader, arch *sys.Arch, syms *sym.Symbols) {
+func (l *Loader) LoadFull(arch *sys.Arch, syms *sym.Symbols) {
 	// create all Symbols first.
 	l.Syms = make([]*sym.Symbol, l.NSym())
 	for _, o := range l.objs[1:] {
@@ -505,7 +503,7 @@ func LoadFull(l *Loader, arch *sys.Arch, syms *sym.Symbols) {
 
 func loadObjSyms(l *Loader, syms *sym.Symbols, r *oReader) {
 	lib := r.unit.Lib
-	istart := l.StartIndex(r)
+	istart := l.startIndex(r)
 
 	for i, n := 0, r.NSym()+r.NNonpkgdef(); i < n; i++ {
 		osym := goobj2.Sym{}
@@ -550,10 +548,10 @@ func loadObjSyms(l *Loader, syms *sym.Symbols, r *oReader) {
 
 func loadObjFull(l *Loader, r *oReader) {
 	lib := r.unit.Lib
-	istart := l.StartIndex(r)
+	istart := l.startIndex(r)
 
 	resolveSymRef := func(s goobj2.SymRef) *sym.Symbol {
-		i := l.Resolve(r, s)
+		i := l.resolve(r, s)
 		return l.Syms[i]
 	}
 
@@ -735,7 +733,7 @@ func loadObjFull(l *Loader, r *oReader) {
 				Parent:   inl.Parent,
 				File:     resolveSymRef(inl.File),
 				Line:     inl.Line,
-				Func:     l.SymName(l.Resolve(r, inl.Func)),
+				Func:     l.SymName(l.resolve(r, inl.Func)),
 				ParentPC: inl.ParentPC,
 			}
 		}
@@ -754,6 +752,8 @@ func loadObjFull(l *Loader, r *oReader) {
 	}
 }
 
+var emptyPkg = []byte(`"".`)
+
 func patchDWARFName(s *sym.Symbol, r *oReader) {
 	// This is kind of ugly. Really the package name should not
 	// even be included here.

src/cmd/link/internal/loadmacho/ldmacho.go

@@ -10,7 +10,7 @@ import (
 	"cmd/internal/bio"
 	"cmd/internal/objabi"
 	"cmd/internal/sys"
-	"cmd/link/internal/objfile"
+	"cmd/link/internal/loader"
 	"cmd/link/internal/sym"
 	"encoding/binary"
 	"fmt"
@@ -424,7 +424,7 @@ func macholoadsym(m *ldMachoObj, symtab *ldMachoSymtab) int {
 	return 0
 }
 
-func Load(l *objfile.Loader, arch *sys.Arch, syms *sym.Symbols, f *bio.Reader, pkg string, length int64, pn string) error {
+func Load(l *loader.Loader, arch *sys.Arch, syms *sym.Symbols, f *bio.Reader, pkg string, length int64, pn string) error {
 	lookup := func(name string, version int) *sym.Symbol {
 		// Check to see if we've already defined the symbol.
 		if i := l.Lookup(name, version); i != 0 {